1. Technical Field of the Invention
The present invention generally relates to the field of designing and manufacturing of metallic pipe for conveying drinking-water. More particularly the invention relates to a pipe with an outer metallic pipe and an inner plastic pipe suitable for conveying drinking-water and the connectors for the pipe.
2. Description of the Related Art
Zecchin, et al, in PCT/EP98/08182, disclosed a composite pipe made of metal-plastic for hydro-thermo-sanitary plants and process for the production thereof. The composite pipe consist of an internal metal pipe, an outer pipe made of a plastic suitable for conveying drinking-water, and an intermediate layer having a bi-adhesive function. The outer pipe and the intermediate layer are both extruded onto the inner metal pipe. The material for the outer pipe and the intermediate layer preferably contains an anti-oxidizer additive for the pipe metal. The primary purpose of Zecchin's invention is to prevent corrosions due to the action of local leakage currents and/or chemical corrosion caused by acid substances released from building materials like concrete of the floors in which the pipes are embedded.
David A. Shotts, et al, in U.S. Pat. No. 5,152,323, disclosed a plastic-lined metal pipe which includes an outer metallic pipe having a longitudinal weld and an inner plastic sleeve melt-bonded to the metallic pipe. The metallic pipe is of a size to be in mechanical engagement with the sleeve around the entire circumference of the sleeve. The pipe is manufactured using an extruder, for providing a plastic sleeve, in conjunction with a continuous roll-forming tubing mill production line, for forming and treating the metallic outer tube, so that the lined pipe is made using a continuous process. The plastic sleeve is caused to not collapse during the manufacturing process and the sleeve and pipe are firmly locked together. The pipe may be made by apparatus for continuously manufacturing plastic-lined metal pipe including an extruder for providing a plastic sleeve and a continuous roll-forming tubing mill production line. The production line operates to sequentially deform a substantially flat steel strip to a generally tubular configuration and includes an electric resistance welder or high frequency welder for continuously welding the lateral edges of the moving strip to complete the pipe. A plastic sleeve is fed into the about-to-be-formed metallic pipe upstream of the welder. This plastic sleeve has an outside diameter slightly smaller than the inside diameter of the metallic pipe in the as-formed condition of the sleeve and the sleeve maintains its generally tubular configuration from the time it is inserted into the metal pipe until the manufacture is completed. The production line also includes a station for reducing the inside diameter of the metallic pipe to substantially the outside diameter of the plastic sleeve thereby locking the two components together.
Alexander Esser in U.S. Pat. No. 6,575,197 disclosed a double-layer pipe for fluidic transport of abrasive solids. The pipe includes a hardened inner pipe portion of steel; an outer pipe portion of weldable steel; terminal coupling collars made of weldable steel; and a heat-insulating layer disposed between the inner pipe portion and the outer pipe portion. The pipe includes a heat-insulating layer between the inner pipe portion and the outer pipe portion to form a barrier during heating of the inner pipe portion to thereby prevent heat from dissipating to a significant degree from the inner pipe portion to the outer pipe portion. The applied heat remains in the inner pipe portion so that the inner pipe portion, especially when thin pipe walls are involved, can be heated evenly within a very narrow temperature window. When the inner pipe portion is then quenched, a markedly even hardness is realized over the entire circumference as well as length of the inner pipe portion. The heat-insulating layer disposed between the inner pipe portion and the outer pipe portion may be formed by a coating made of a combustible non-metallic material and applied upon the outer surface of the inner pipe portion and/or the inner surface of the outer pipe portion.
John Werner in U.S. Pat. No. 4,507,842 disclosed an improved method for sealing and protecting a plastic lined pipe joint. The improved plastic collar seal is placed in the interior of a pipe joint formed between first and second externally threaded plastic lined pipe sections which are to be held together by an internally threaded pipe collar. The improved plastic collar seal is a hollow, open ended, cylindrical plastic collar seal presized to concentrically fit within the plastic liner of the sections of plastic lined pipe with minimum concentric tolerance. The open ends of the plastic collar seal are internally beveled and the plastic collar seal is equipped with external O-ring grooves and O-rings at each of the ends. The collar seal is further provided with an external ledge or ridge molded concentrically to the collar seal between the O-rings wherein the ledge is adapted to fit within the internally threaded collar and rest on the end of the lined pipe. This ledge is positioned such that the distance from at least one end of the collar seal to the ledge exceeds the length of the internally threaded collar. In operation, the collar is threaded on the first plastic lined pipe section and the improved plastic collar seal is inserted within the pipe section and collar with the ledge coming to rest on the end of the pipe section leaving the other end of the plastic collar seal extending beyond the collar. The second section of plastic lined pipe can then be easily threaded into the internally threaded collar, over the collar seal, thus forming a tight pipe joint with the collar seal within the joint.
John J. Hunter in U.S. Pat. No. 4,709,946 disclosed a pipe joint which secures two lined pipe sections together and seals the juncture of the pipe sections against the migration of fluids through the joint and methods for forming the pipe joint. The method includes the steps of axially aligning first and second pipe sections; securing the first pipe section to the second pipe section; overlapping the liners of the first and second pipe sections; and compressing the liners of the first and second pipe sections where overlapped to seal the joint against migration of pressurized fluids through the joint. The pipe joint provided by this method includes, in one embodiment, first pipe means having a fluid impervious first liner mounted on the interior thereof; second pipe means having a fluid impervious second liner mounted on the interior thereof; means for securing said first pipe means in axial alignment with said second pipe means wherein said first liner and said second liner are partially overlapped; and means for compressing said first and second liners were overlapped to seal the pipe joint formed at the juncture of said first and second pipe means for the transmission of fluids there through.
What is desired is a plastic-lined metallic pipe with a food-grade non-poisonous inner plastic lining pipe and an outer metallic pipe made of high strength, light-weight and corrosion resistant aluminum alloy.